X-ray imaging systems are conventionally used for examining objects of interest, particularly in medical applications. Recently, an improved X-ray imaging method referred to as grating-based differential phase-contrast imaging (DPCI) has been proposed by F. Pfeiffer et al., Phys. Rev. Lett. 98(10), 108105, 2007. An example of a differential phase-contrast imaging system is described in WO 2010/109368 A1.